Message: Clean up unit tests and improve code coverage

Message: Clean up unit tests and improve code coverage

* Remove unnecessary use of ReflectionClass. It was testing
  internal properties that aren't part of the API. Using the
  getters instead.

* Remove need for func_get_args that was making the test more
  complex and the data provider hard to read. Simply maintain
  it as array of expected params and array of variadic arguments.

* Rename tests to more closely match tested methods.

* Rename data providers to provide*, and make them static.

* Reorder tests to more closely match logical order of the class.

* Improve line coverage from 31% to 67%.

Also:
* Remove testParams (dupes testConstructorParams).
* Add tests for RawMessage class.
* Add tests for transformation and parsing.
* Add tests for wfMessage().
* Add tests for Message::newFrom*.
* Add tests for "$*" replacement.
* Add tests for __toString.

Change-Id: I2b183a66f9e9f51bd800088e174b1ae4d3284d8d